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For many years, the idea that coronal mass ejections (CME) launched from
the Sun and could strike the Earth was inferred from an indirect chain of
evidence collected from multiple satellites. Now the Heliospheric Imagers
aboard the STEREO-A spacecraft has managed to view a CME propagate from
the surface of the Sun to the Earth.
Plasma from solar flares or coronal mass ejections travel along solar wind
to ultimately produce aurora's in Earth's polar regions, and affect
satellites and power grids and other man-made electronics. Of course, a
CME affects the propagation of radio waves that we radio communicators
transmit and receive.
This visualization shows the position of the STEREO spacecraft during the
event, as well as the positions of the inner solar system planets, Venus
and Mercury. A faint cone illustrates the field-of-view (FOV) of the HI-2
imager on STEREO-A. The position of the front of the CME is computed from
STEREO data.
NASA's STEREO spacecraft and new data processing techniques have succeeded
in tracking space weather events from their origin in the Sun's ultra-hot
corona to impact with the Earth 96 million miles away, resolving a 40-year
mystery about the structure of the structures that cause space weather:
how the structures that impact the Earth relate to the corresponding
structures in the solar corona.
Despite many instruments that monitor the Sun and a fleet of near-earth
probes, the connection between near-Earth disturbances and their
counterparts on the Sun has been obscure, because CMEs and the solar wind
evolve and change during the 96,000,000 mile journey from the Sun to the
Earth.
STEREO includes "heliospheric imager" cameras that monitor the sky at
large angles from the Sun, but the starfield and galaxy are 1,000 times
brighter than the faint rays of sunlight reflected by free-floating
electron clouds inside CMEs and the solar wind; this has made direct
imaging of these important structures difficult or impossible, and limited
understanding of the connection between space storms and the coronal
structures that cause them.
Newly released imagery reveals absolute brightness of detailed features in
a large geoeffective CME in late 2008, connecting the original magnetized
structure in the Sun's corona to the intricate anatomy of an
interplanetary storm as it impacted the Earth three days later. At the
time the data were collected, in late 2008, STEREO-A was nearly 45 degrees
ahead of the Earth in its orbit, affording a very clear view of the
Earth-Sun line.
Video is here:
<http://www.youtube.com/watch?v=NVD3OnigFFE>
--
Tomas David Hood
Hamilton, Montana
<http://nw7us.us/> and <http://tomas-david-hood.com/>
Contributing editor, Propagation Columns:
CQ Magazine, CQ VHF, Popular Communications
<http://sunspotwatch.com/>
Facebook:
<http://www.facebook.com/spacewx.hfradio>
<http://www.facebook.com/NW7US>
Twitter Space WX : @hfradiospacewx
Twitter NW7US : @NW7US
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